Cancer develops as a result of the accumulation of multiple genetic changes in somatic cells, all of which cooperate in inducing the transformed phenotype. In acute myeloid leukemia (AML) the number and nature of these "cooperating" oncogenic mutations is most often unknown. The BXH-2 mouse offers a model system ideal for the elucidation of interacting gene mutations. In this model, a Murine Leukemia Virus (MuLV) induces AML by acting as an insertional mutagen. The number of different gene whose expression is altered by proviral insertion and which contribute to leukemia development in BXH-2 mice is likely to be large. At least eight different loci have been identified which are mutated by proviral insertion in multiple BXH-2 leukemias, but none of these loci is involved in more than 15% of the leukemias. Therefore, new and more efficient methods for identifying and cloning these cancer genes have been developed. These techniques include the selection of tumor-specific, somatically-acquired proviruses near CpG islands, which greatly enriches for proviruses near genes involved in leukemogenesis, and the development of a highly efficient inverse PCR-based approach for cloning proviral insertion sites. The combination of these two technologies allows rapid progress toward the goal of understanding the complex network of genes mutated during myeloid leukemia development. These procedures have been used to identify mutations in two genes likely to impact the same cell signaling pathway: Nf1 and Cdc251. It is the goal of this proposal to define the overlap between the oncogenic effects of these mutations and discover other proteins involved in this pathway.